Transcript Chapter 11 – Part 4 The Cardiovascular System

Chapter 11 – Part 5
The Cardiovascular System
Vital Signs
 The following measurements are referred
to collectively as vital signs in clinical
settings:
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Arterial pulse
Blood pressure
Respiratory rate
Body temperature
 Vital signs are a fairly good indication of the
efficiency of a person’s circulatory system
Pulse
 Pulse – Pressure wave
of blood
 Is created from the
alternating expansion
and recoil of an artery
that occurs with each
beat of the left
ventricle
Pressure Points
 Monitored at pressure
points where pulse is
easily palpated
 Can feel a pulse where an
artery lies close to the
body surface
 Are called pressure points
because these same
points are compressed to
stop blood flow during
hemorrhage
Pulse
 Normally pulse rate
(pressure surges per
minute) equals heart
rate (beats per minute).
 Pulse averages 70-76
beats per minute in a
normal resting person.
 Pulse is influenced by
activity, postural
changes, and emotions.
How to Take a Pulse
 Place the tips of your
first two or three fingers
over one of the arteries
designated as a pressure
point.
 Compress the artery
firmly as you begin and
then immediately ease
up on your pressure
slightly.
Blood Pressure
 Blood Pressure – The pressure
the blood exerts against the
inner walls of the blood
vessels
 It is the force that keeps blood circulating
continuously even between heartbeats
 Any system equipped with a pump that forces fluid
through a network of closed tubes operates under
pressure.
 Understood to mean the pressure within the large
systemic arteries near the heart
Blood Pressure Gradient
 Blood flows along a pressure gradient (from
high to low) as it makes its circuit.
 Pressure is highest in the large arteries and
continues to drop throughout the pathway,
reaching zero or negative pressure at the venae
cavae
 The high pressure in these arteries forces the
blood to continually move into areas where the
pressure is lower.
Comparison of Blood Pressures in Different
Vessels
Blood Pressure Gradient
 The pressure differences between arteries
and veins are apparent when the vessels are
cut:
 If a vein is cut - the blood flows evenly
from the wound
 If an artery is cut - rapid spurts of blood
Blood Pressure Gradient
 The continual flow of blood absolutely depends on
the stretchiness (elasticity) of the large arteries
and their ability to recoil and keep the pressure on
the blood.
 Garden hose example with hard walls:
 When the water hose is turned on, the water spurts
out under high pressure because the hose walls don’t
expand.
 When the faucet is suddenly turned off, the flow of
water stops because the walls cannot recoil to keep
pressure on the water. The pressure drops and the
flow of water stops.
Measuring Blood Pressure
 Two arterial blood pressure
measurements are usually made:
1. Systolic Pressure – Pressure in
the arteries at the peak of
ventricular contraction
2. Diastolic Pressure – Pressure in
the arteries when the ventricles
are relaxing
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Blood pressures are reported in
millimeters of mercury (mm Hg)
Measuring Blood Pressure
 A blood pressure of
120/80 indicates a:
 Systolic pressure of 120
mm Hg
 Diastolic pressure of 80
mm Hg
Measuring Arterial Blood Pressure
Blood Pressure: Effects of Factors
 Arterial blood pressure is
directly related to the two
following factors. An
increase in the following
factors causes an increase in
blood pressure.
1. Cardiac output (the
amount of blood
pumped out of the left
ventricle per minute)
2. Peripheral resistance
Blood Pressure: Peripheral Resistance
 Peripheral Resistance –
The amount of friction
encountered by the blood
as it flows through the
blood vessels
 It is increased by the
constriction, or narrowing,
of the blood vessels.
 Increased blood volume or
thickness (viscosity)
increases peripheral
resistance.
Blood Pressure: Effects of Factors
 Many factors can alter blood pressure.
Some of the factors include:
 Age
 Weight
 Time of day
 Exercise
 Body position
 Emotional state
 Various drugs
Blood Pressure: Effects of Factors
1. Neural Factors: Autonomic Nervous System
 Sympathetic nerves cause vasoconstriction, which
increases blood pressure back to homeostatic levels
 This hopefully increases venous return so circulation can
continue.
 During exercise:
 There is a general vasoconstriction
except in the skeletal muscles.
 The vessels of the skeletal muscles
dilate to increase the blood flow to
the working muscles.
Blood Pressure: Effects of Factors
2. Renal factors
 Regulates blood pressure by altering blood volume
 As blood volume decreases, blood pressure
decreases.
 As blood volume increases, blood pressure
increases.
Blood Pressure: Effects of Factors
3. Temperature
 Heat has a vasodilation effect
 Warm compresses are used to
speed the circulation into an
inflammed area
 Cold has a vasoconstricting effect
 Why cold compresses are
recommended to prevent
swelling of a bruised area
Blood Pressure: Effects of Factors
4. Chemicals
 Various substances can cause increases or decreases
 Nicotine increases blood pressure by causing
vasoconstriction
 Alcohol causes vasodilation and decreases the blood
pressure; often become flushed after drinking alcohol
5. Diet
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A diet low in salt, saturated fats, and
cholesterol helps to prevent high blood
pressure
Factors Determining Blood Pressure